Antibacterial, antibiofilm, and antioxidant activities of two novel metal–organic frameworks (MOFs) based on 4,6-diamino-2-pyrimidinethiol with Zn and Co metal ions as coordination polymers

In the present era, the increase in free radical species (FRs) and multidrug-resistant (MDR) bacteria represents a major worldwide concern for public health. Biofilm development and the overuse and misuse of antibiotics could lead to the adaptation of bacteria to antimicrobial agents. Consequently, finding novel multifunctional species with antibacterial, antioxidant, and antibiofilm properties has become crucial in the fight against challenging bacterial infections and chronic inflammatory conditions. Metal–organic frameworks (MOFs) with zinc and cobalt metal centers are widely utilized in biological and environmental remediation owing to their versatility. In this study, multifunctional Zn-MOFs and Co-MOFs were successfully synthesized with zinc and cobalt as metal centers and 4,6-diamino-2-pyrimidinethiol as an organic linker using a hydrothermal technique. Numerous characterization techniques were used to fully examine the MOF structure, functionality, chemical makeup, crystalline structure, surface appearance, thermal behavior, and magnetic characteristics; the techniques included XPS, PXRD, FTIR, FESEM, EDX, UV-visible, BET, BJH, TGA/DTG, DSC, and magnetic susceptibility measurement. The antioxidant, antibacterial, and antibiofilm activities of the MOFs were examined, and they demonstrated potent activity in each of these aspects. The proposed mechanisms of antibacterial activity suggest that bacterial cell death results from multiple toxic effects, including electrostatic interaction and lipid peroxidation, when MOFs are attached to bacteria, leading to the formation of reactive oxygen species (ROSs). Zn-MOFs exhibit high antibacterial and antibiofilm efficacy owing to their large surface-to-volume ratio and porous nature, while Co-MOFs exhibit high antioxidant capacity owing to their redox properties.


Fig. 1S
Fig. 1S Disc diffusion assay for antibiotic susceptibility testing using the Kirby-Bauer method against the following bacterial strains: (A) Staphylococcus aureus ATCC 6538, (B) clinical isolates of Staphylococcus aureus, (C) Clinical isolate of Pseudomonas aeruginosa, and (D) Pseudomonas aeruginosa ATCC 9027.

Fig
Fig. 4S MBC assay of the Co-MOF against four bacterial species.

Fig
Fig. 5S MBC assay of the Zn-MOF against four bacterial species.

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Fig. 6S Antibiofilm and an antioxidant assay of the MOFs.

Fig
Fig. 7S EDX elemental surface mapping of synthesized Co-MOF.

Table 2S .
XRD data were used to calculate microstrain and crystallite size based on FWHM using the Scherrer equation for Co-MOF.

Table 3S .
Antibiotics susceptibility test based on Kirby-Bauer test method used for all the bacteria.

Table 4S
. OD of the Zn-MOF against clinical isolates of Staphylococcus aureus (A & B) and Pseudomonas aeruginosa (E & F), as well as their standard strains (Staphylococcus aureus ATCC 6538 (C & D) and Pseudomonas aeruginosa ATCC 9027 (G & H)).

Table 5S .
OD of the Co-MOF against clinical isolates of Staphylococcus aureus (A & B) and Pseudomonas aeruginosa (E & F), as well as their standard strains (Staphylococcus aureus ATCC 6538 (C & D) and Pseudomonas aeruginosa ATCC 9027 (G & H)).

Table 6S .
OD and percentage inhibition of the biofilm provided by the Zn-MOF.

Table 7S .
OD and percentage inhibition of the biofilm provided by the Co-MOF.

Table 8S .
Absorbance and percentage inhibition of DPPH provided by the MOFs.

Table 9S .
Zinc and Cobalt Ions Leaching from MOFs under Various pH Conditions.